Special to Hawaii 24/7 by Gary Sanders | TMT Project Manager

For five years, we designed and developed a generic version of the TMT observatory. As we studied five excellent sites in Chile, Mexico, and Hawaii, we designed carefully in a way that straddled site conditions, not knowing which site would be chosen.

It is common in large projects to develop a “site independent” design. To be sure, when the TMT Board narrowed the choice to Cerro Armazones in Chile and Mauna Kea in Hawaii, our straddle became somewhat easier. In July 2009, with Mauna Kea selected, we began the “site specific” adjustments to the TMT design.

Gary Sanders

Nearly every subsystem in TMT was touched by this, though the facilities, enclosure, and the design of operations were most affected. Mauna Kea has snow. Armazones does not.

The weather sealing of the enclosure and the features enabling snow removal from the enclosure may seem like simple matters compared to the challenge of adaptive optics. But designing for the right response to snow can mean quicker recovery from storms and this adds significant observing efficiency for TMT.

Humidity and altitude are higher at Mauna Kea. Mirror position sensors must be designed for the humidity. Power, cooling, and ventilation systems must be designed for the thinner air. This often means derating the equipment and installing additional units. The mature infrastructure for astronomy gathered about Mauna Kea simplifies many aspects of operations and reduces the scope of the facilities to construct. Nearly 20 kilometers of road needed in Chile could be dropped from our construction and maintenance plans.

The logistics of the construction campaign change. How many sea containers can be handled by local ports? How many barges arrive with supplies? Warehouses? Road systems for transporting large and fragile loads? Import and ocean freight fees? Where will construction workers live during the project? How many local machine shops and parts suppliers are able to support real-time needs? What are the specific local labor rates and costs for power and other services?

One of the most important aspects of designing TMT for Mauna Kea is respecting the sacred place that Mauna Kea has in the Polynesian culture. Designing TMT cannot just be an engineering matter. Placing TMT on Mauna Kea raises concerns for some Hawaiians. We have worked hard to mitigate these concerns in designing TMT.

The process established to guide this in Hawaii involves working with the Design Review Committee of the Office of Mauna Kea Management. Beginning with simple site, facility and enclosure sketches, in a series of meetings over the last year, we iterated in a cooperative and constructive manner to produce an observatory design that is more compact, colored, and coated to be less visible, placed to respect the terrain, and sited to avoid culturally and biologically significant attributes of Mauna Kea. This led to approval of the TMT design by the Mauna Kea Management Board.

This design has been described, with its impacts and proposed mitigations, in a Hawaii Environmental Impact Statement (EIS) prepared ably by Parsons Brinckerhoff. The EIS has been carefully aligned with the Comprehensive Management Plan for Mauna Kea recently approved by the State of Hawaii Board of Land and Natural Resources.

The third week of May was a gratifying week. At a public hearing of the Mauna Kea Management Board, the motivation for TMT, and the results of this intensive design iteration were presented to the Board. Public comments were made, supporting and opposing TMT’s placement on Mauna Kea.

At the conclusion of the hearing, the Board recommended that TMT be approved by the University of Hawaii Board of Regents. On the same day, the Governor of Hawaii approved the TMT EIS.

These are encouraging and important steps in moving toward permission to construct TMT, and in defining a Hawaii version of TMT. We now know what the site specific TMT will look like. And we have worked hard to respect the cultural setting for this great observatory.

— Find out more:
www.tmt.org